Generally, the cutting of hard materials such as silicon wafers may be performed by means of a steel wire having abrasive particles (for example, made of diamond) at its periphery.
To solve possible wire breaks, prior art advocates the use of a steel wire having a high carbon content.
Abrasive particles are bonded to the wire by means of a resin or metal binder layer. Such a binder maintains the particles at the surface of the wire to give abrasive properties thereto.
Generally, and conversely to the binder, the particles are made of a material harder than the material to be cut.
Indeed, at the first use of the wire, the binder is partly eroded to expose the abrasive particles. The sawing of the material is then performed by repeated passages of the cutting wire on the surface of the material to be cut, that is, by friction of the protruding portions of the abrasive particles on the material.
Once the protruding portions of the abrasive particles have been exposed, the binder no longer comes in direct contact with the material to be cut. However, it may wear according to the two following mechanisms:                by mechanical deformation: on sawing of a material, the abrasive particles are alternately pushed forward and backward and along the main direction of the wire. This motion is the direct consequence of the friction with the material being cut. Thus, the binder deforms a little for each movement. At the end of the cutting, the binder may be locally too deformed to efficiently retain the abrasive particles at the surface of the wire.        by abrasion/erosion: this mechanism results from the presence of fragments of the material to be cut located between the binder—which displaces along with the wire—and the material to be cut. Due to the sawing movements, the fragments of material erode the binder, with, as a consequence, a progressive decrease of its thickness. At the end of the cutting, the binder is no longer thick enough to efficiently retain the abrasive particles at the surface of the wire. The abrasive particles detach, which progressively decreases the abrasive power of the wire and thus its ability to cut a material.        
Generally, mechanical deformation is a stronger phenomenon than the abrasion of the binder.
To delay or even to suppress the deterioration of the abrasive properties of the wire, binders based on metal alloys have been developed. They appear to have better hardness properties than a resin.
Thus, to limit the wearing of the wire, a binder based on a nickel and phosphorus alloy may be used. The binder is chemically deposited at the wire surface to cover abrasive grains. Further, its hardness is greater than that of pure nickel.
To limit the cracking of the bonding layer, document EP 2 428 317 advocates limiting the sulfur, oxygen, and hydrogen contents in the electrolytic nickel deposit.
Other solutions comprise using a binder made of cobalt/nickel alloy. Now, the electrodeposition of this type of nickel/cobalt involves compounds such as nickel sulfate, which is carcinogen. Further, metal nickel may cause allergies.
Metal binders may generally corrode in contact with water which is brought into the cutting area. Since this phenomenon of course adversely affects the lifetime of the abrasive wire, the corrosion of the binding metal is desired to be avoided by those skilled in the art.
The wire and the binder should thus meet certain requirements.
Preferably, the binder should not crack during the wire use. When the wire is stretched, at its maximum stress limit, the surface of the binder should not crack.
There thus is a need to develop alternatives to such binders, especially to ensure the maintaining of the abrasive grains on the core of an abrasive wire, but also to control the wearing and the degradation of the binder. The present invention aims at solving this technical problem.